EP3453453B1 - Substrate - Google Patents

Description

Various problems arise when coating ceramic or metallic honeycomb bodies / filters, hereinafter called the substrate, with liquid coating media.

One possibility of coating the substrates is to contact them with the openings provided on one side with the coating medium provided and to draw the liquid coating medium through the channels of the substrate by applying a negative pressure to the opposite side of the substrate. If only one coating of the ducts is to be carried out over part of their length, it is disadvantageous that the inevitably created flow profile coats different ducts up to a different length.

If the coating medium is pressed into the channels by gravity pressure, it must be checked (usually with a sensor) when the liquid escapes from the top when the channels are completely coated. When coating on part of the length of the channels, the height of the liquid column of the coating medium inside the channels is determined by sensors. However, this method does not work if the substrate is made of conductive or semiconducting materials such as metals or silicon carbide.

Another disadvantage is that the coating media mostly contain ceramic particles, which have an abrasive effect and cause high wear on pumps for transporting the coating medium (e.g. piston pumps).

The EP1273344A1 relates to a process for the production of zoned coated substrates for exhaust gas catalysts.

The object of the present invention was to provide coated substrates which do not have the disadvantages of the prior art.

This object is achieved by specifying a coated substrate for producing exhaust gas filters for motor vehicles, in which the channels are provided on the inside with at least one catalytically active coating, the coated length of the channels is less than the axial length L of the substrate and at least 95% of the channels of a substrate, the coated length of the channels does not differ from one another by more than 5 mm, the channels being provided on the inside with at least a first catalytically active coating and a second catalytically active coating, the first catalytically active coating and the second catalytically active coating coated lengths of the channels is in each case smaller than the axial length L of the substrate and, in at least 95% of the channels of a substrate, the lengths of the channels respectively coated with the first catalytically active coating and the second catalytically active coating are not more than 5 mm apart soften, and the distance between the two coatings is at least 5 mm in at least 95% of the channels of a substrate.

Detailed description of the invention

The coated substrate according to this invention can be produced by an arrangement for coating substrates with liquid coating media (113, 213), which has a cylinder (102, 202) filled with a liquid (103, 203) with a piston (101, 201) The cylinder (102, 202) filled with a liquid communicates with a container (112, 212), in the interior of which a displacement body (111, 211) is arranged such that the displacement body (111, 211) when the piston moves (101, 201) is moved proportionally by the liquid (103, 203), and the container (112, 212) communicates with the coating device (122, 222) for the substrate (121, 221), the displacement body (111, 211 ) acts on the liquid coating medium (113, 213), so that a proportional change in the fill level of the liquid coating medium (113, 213) in the coating device (122, 222) is effected.

The piston (101, 201) is advantageously moved by an electrical actuator (100, 200). For this purpose, for example, an electric motor provided with a toothed wheel can be used, which moves a piston provided with a toothed rack.

The substrate (121, 221) is generally a hollow substrate which consists of metals or ceramics and has at least one inner channel (110, 210, 310), usually a multiplicity of inner channels. The substrates are generally essentially cylindrical support bodies, each of which has a cylinder axis, two end faces, a lateral surface and an axial length L and are crossed by a plurality of channels from the first end face to the second end face. Such support bodies are often referred to as honeycomb bodies. In particular, the substrates can be flow-through honeycomb bodies, which can have a high cell density (number of inner channels per cross-sectional area) of approximately 10 cm ^-2 to 250 cm ^-2 , but wall-flow filters can also be used. The substrate can consist, for example, of cordierite, mullite, aluminum titanate, silicon carbide or metals such as steel or stainless steel. The substrate is advantageously a monolithic, cylindrical shaped catalyst carrier and is traversed by a large number of flow channels for the exhaust gases of internal combustion engines, which are parallel to the cylinder axis. Such monolithic catalyst carriers are used on a large scale for the production of automotive exhaust gas catalysts. The cross-sectional shape of the catalyst carrier depends on the installation requirements for the motor vehicle. Catalyst bodies with a round cross section, elliptical or triangular cross section are widespread. The flow channels usually have a square cross section and are arranged in a narrow grid over the entire cross section of the catalyst body. Depending on the application, the channel or cell density of the flow channels usually varies between 10 and 250 cm ^-2 . For the exhaust gas purification of passenger cars, catalyst carriers with cell densities of about 62 cm ^-2 are still often used today. The substrate is advantageously arranged liquid-tight on the coating device, which is brought about by at least one seal can. The seal can be hollow and can be filled with gas or liquid and sealed when it is placed on or inserted into the coating device. The tightness of the connection can be checked by a pressure or flow sensor.

The displacement body (111, 211) is a hollow body which expands and contracts again by the action of pressure and can be made of any elastic material such as rubber, plastic or metal, the material being opposite the liquid (103, 203) and the liquid Medium (113, 213) must be inert.

The liquid does not have to meet any special requirements, but should not have a corrosive or abrasive effect and should not change its properties under the conditions of use. Hydraulic oil or water are suitable, for example.

The liquid coating medium (113, 213) is, for example, a suspension or dispersion for coating exhaust filters for motor vehicles ("washcoat"), which contains catalytically active components or their precursors and inorganic oxides such as aluminum oxide, titanium dioxide, zirconium oxide or combinations thereof, the oxides can be doped with silicon or lanthanum, for example. Oxides of vanadium, chromium, manganese, iron, cobalt, copper, zinc, nickel or rare earth metals such as lanthanum, cerium, praseodymium, neodymium, promethioum, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium can be used as catalytically active components Ytterbium or combinations thereof can be used. Precious metals such as platinum, palladium, gold, rhodium, iridium, osmium, ruthenium and combinations thereof can also be used as catalytically active components. These metals can also be present as alloys with one another or other metals or as oxides. In the liquid coating medium, the metals can also be present as precursors, such as nitrates, sulfites or organyls of the noble metals mentioned and their mixtures, in particular palladium nitrate, palladium sulfite, platinum nitrate, platinum sulfite or Pt (NH ₃ ) ₄ (NO ₃ ) ₂ can be used. By calcination at about 400 ° C to about 700 ° C, the catalytically active component can then be obtained from the precursor. To coat a substrate for the production of automotive exhaust gas catalysts, it is first possible to coat with a suspension or dispersion of an inorganic oxide and in a subsequent coating step with a suspension or dispersion which contains one or more catalytically active components. However, the liquid coating medium can also contain both of these components. The liquid coating medium often has a solids content between 35 and 52% and viscosities between 15 and 300 cps.

The geometry of the displacement body (111, 211) can be adapted to the inner shape of the container (112, 212), but this is not absolutely necessary. On the one hand, a bellows with a square or circular base can be used in a container with a corresponding inner shape and thus act as a hydraulically expandable stamp on the liquid coating medium (113, 213). Likewise, the displacement body (111, 211) can also be designed as a spherical rubber bubble, which acts on the liquid coating medium (113, 213) without any particular adaptation to the internal geometry of the container. The displacement body (111, 211) can essentially completely fill the container, but this does not necessarily have to be the case as long as the displacement body (111, 211) is sufficiently large around the coating device (122, 222) and the volume of the substrate to be coated (121, 221) with liquid coating medium. Apart from the openings with which it communicates with the cylinder (102, 202) and the coating device (122, 222), the container (112, 212) must be sealed or closable from the environment. However, the container (112, 212) advantageously has inlets for liquid coating medium (113) or liquid (203) and can advantageously be opened or dismantled for maintenance and cleaning purposes.

The cylinder (102, 202) can communicate with the container (112, 212) in different ways. On the one hand, the liquid in the The interior of the displacement body (111) and the liquid coating medium (113) are located outside the displacement body (111) in the container (112), so that the closed outer sides of the displacement body (111) act on the liquid coating medium (113). A pressure is generated in the container through which the liquid medium (113) is conveyed through an opening from the container via a line (114) into the coating device (122).

In a further embodiment, the liquid (203) outside the displacement body (211) in the container (212) and the liquid coating medium (213) inside the displacement body (211), so that the closed inside of the displacement body (211) on the liquid Act coating medium (213) and the liquid coating medium (213) is conveyed through an opening from the container (212) via a line (214) into the coating device (222).

In a further embodiment, the coating device (122, 222) is equipped with sensors (123, 223) which react to the fill level of the liquid coating medium (113, 213).

Suitable sensors can be a refractive index sensor which reacts to the change in the refractive index when the liquid level rises, a conductivity sensor or simply a light barrier.

These sensors are advantageously connected to a control unit (115, 215) which controls the movement of the piston (101, 201) and processes the signal transmitted by the sensors (123, 223) to control the movement of the piston, so that a reproducible fill level (130, 230) of the liquid coating medium (113, 213) in the coating device (122, 222) can be ensured regardless of the amount of the liquid coating medium (113, 213). If several substrates (121, 221) are coated one behind the other, the amount of liquid coating medium (113, 213) in the arrangement is successively reduced with each coating process, so that with the same process parameters the liquid level in the coating device (122, 222) drops. By using the sensors (123, 223), this effect can be compensated and a constant liquid level can be ensured even when refilling liquid coating medium. By using a suitable control unit (125, 225), which processes the signal from the sensors and controls the piston (101, 201) or the preferably electrical actuator (100, 200) used to actuate the piston, the specified fill level (130, 230) of the liquid coating medium (113, 213) in the coating device (122, 222) can be set automatically.

The arrangement for producing the coated substrates can also have a sensor for monitoring the position of the displacement body. For example, a light barrier (124, 224), an ultrasonic sensor or a mechanical sensor (e.g. rocker arm switch) can be used to monitor the expansion or position of the displacement body. If the displacement body has a leak, this can be determined because the displacement body in this case no longer returns completely to its starting position or expands completely. Such a sensor then indicates such an event.

The arrangement can also have a sensor for monitoring the liquid level (123, 232) of the liquid coating medium within the substrate (121, 221). In this way, the supply of liquid coating medium into the substrate can be interrupted if the substrate has been coated to the desired substrate length. However, such a sensor is not always necessary, since it is an advantage of the arrangement according to the invention that this monitoring no longer has to be carried out if the internal volume of the substrate is known. However, it can be advantageous if such a sensor for calibrating the arrangement is present.

The invention relates to a coated substrate for producing exhaust gas filters or exhaust gas purification catalysts, in particular for motor vehicles, in which the channels are provided on the inside with a catalytically active coating, the coated length of the channels is less than the axial length L and in at least 95% of the channels of a substrate, the coated length of the channels does not deviate from one another by more than 5 mm, preferably 3 mm. Exhaust filters in the sense of the invention can be made both of flow-through honeycomb bodies, which only purify the exhaust gases chemically but not mechanically (such as, for example, removing soot), but also e.g. from wall-flow filters, the exhaust gases being passed through the porous walls of the flow channels, as a result of which chemical and mechanical purification of the exhaust gases takes place.

The channels of the substrates are not coated over the entire axial length L, but, as described above, only over part of their length. It is advantageous here if the length over which the channels are coated on the inside is essentially the same for as many channels as possible. After the channels of the substrates have been coated internally with the arrangement described, these substrates are then dried and subjected to at least one heat treatment.

The finished substrates suitable for the production of exhaust gas filters for motor vehicles have a particularly uniform coating, which is characterized in that the coated lengths of the different channels do not differ from one another by more than 5 mm, in particular 3 mm, which for at least 95% of all channels one Substrate applies, advantageously at least 99% of all channels of a substrate, in particular at 100% of all channels. Defects can mean that the flow and pressure conditions of individual channels of a substrate deviate significantly from the other channels, which means that the liquid coating medium penetrates considerably more or more easily and under the coating conditions either to a lesser or greater length of the individual Channels is coated. In these cases, the one you want uniform coating length can only be achieved in some of the channels, but generally in more than 95% of all channels.

A method for coating substrates can be carried out with the arrangement described.

• Bereitstellen des Substrates;
• Bereitstellen einer Anordnung gemäß der Erfindung;
• Anordnen des Substrates auf der Beschichtungsvorrichtung;
• Auslösen der Bewegung des Kolbens, so dass die vom Kolben verdrängte Flüssigkeit den Verdrängungskörper proportional zur Menge des verdrängten Flüssigkeitsvolumens bewegt;
• Einwirken des Verdrängungskörpers auf das Beschichtungsmedium, wobei ein der Bewegung des Verdrängungskörpers proportionales Volumen des Beschichtungsmediums verdrängt und ein entsprechender Anstieg des Füllstandes des Beschichtungsmediums in der Beschichtungsvorrichtung bewirkt wird;
• Eindringen des Beschichtungsmediums in die Kanäle des Substrates bis zur gewünschten Füllhöhe bzw. beschichteten Länge der Kanäle proportional zum verdrängten Volumen des Beschichtungsmediums;
• Entfernen des Beschichtungsmediums aus den Kanälen des Substrates, wobei sich die Beschichtung in den Kanälen ausbildet.

This method for coating substrates has the following steps:

• Providing the substrate;
• Providing an arrangement according to the invention;
• Placing the substrate on the coating device;
• Triggering the movement of the piston so that the liquid displaced by the piston moves the displacer in proportion to the amount of the displaced liquid volume;
• Action of the displacement body on the coating medium, displacing a volume of the coating medium proportional to the movement of the displacement body and causing a corresponding increase in the fill level of the coating medium in the coating device;
• Penetration of the coating medium into the channels of the substrate up to the desired filling height or coated length of the channels in proportion to the displaced volume of the coating medium;
• Removing the coating medium from the channels of the substrate, the coating forming in the channels.

The removal of the coating medium from the channels of the substrate is brought about by applying a pressure gradient, as a result of which excess coating suspension is removed after the supply of coating medium to the substrate has been interrupted.

The removal of the coating medium can be effected by pulling back the plunger (101, 201), since this lowers the fill level of the coating medium in the coating device (122, 222) and the substrate (121, 221), which creates the pressure drop and the excess coating medium the channels of the substrate is removed. The removal of the coating medium can, however, also be effected according to the known methods of the prior art, which is described below.

For example, a vacuum can be applied to the lower end faces by opening a valve to an evacuated vacuum container, for example. At the same time, air or another, the coated substrate and the coating suspension against inert gas such as nitrogen can be supplied to the upper end faces without pressure from the upper end faces of the substrate. As the pressure in the vacuum container drops, the flow velocity of the gas in the channels of the substrates also decreases. Such a procedure is, for example, in the EP-A1-941763 , Page 4, line 56 to page 5, line 36, to which reference is made.

However, the procedure can also be reversed and the vacuum applied to the upper end faces and the gas supply to the lower end faces of the substrates. Likewise, this supply can also be changed one or more times or reversed, which according to US-B-7094728 causes a more uniform coating of the channels in the substrates.

Instead of applying a negative pressure ("sucking out or sucking out" the substrates), an excess pressure can also be applied ("blowing out" the substrates). For this purpose, air or another, the coated substrates and the coating suspension against inert gas such as nitrogen is supplied to the upper or lower end face under pressure. Those end faces which lie opposite the end faces to which gas pressure is applied must ensure a sufficient outflow of the gas. A vacuum (vacuum) can be applied for this, but this is not absolutely necessary. However, it shouldn't be from the opposite sides a gas or liquid pressure can also be applied in order to ensure a flow rate of the gas which is sufficient to remove excess coating suspension from the channels of the substrates. Similar to the procedure outlined briefly above US-B-7094728 In this case too, the excess pressure can be supplied alternately from the upper and lower end faces.

After removal of the excess coating suspension, the substrates are optionally dried and subjected to a heat treatment (calcined).

The substrates can be dried before the heat treatment. This measure is optional since the substrate is dried anyway in the subsequent heat treatment.

For this purpose, the channels of the substrate can be removed from the coating device, for example from below, against gravity with preheated air at temperatures between 20 and 150 ° C. and speeds of more than 4, preferably 7-10 m / s, for a period of 5 to Is flowed through for 20 s. This type of predrying prior to the heat treatment (calcining) prevents the flow channels from closing and the channels narrowing at the lower end of the substrates, which can often be observed at very high loads. This additional measure makes it possible to load the substrate with a higher coating quantity than usual without the flow channels closing or narrowing during the drying and calcining process. The concentration of the coating dispersion on the substrate can thus be increased by this measure.

The heat treatment is generally carried out at temperatures from approximately 150 ° C. to approximately 800 ° C., in particular at approximately 200 ° C. to 700 ° C., advantageously at approximately 250 ° C. to approximately 600 ° C. The time of the heat treatment is approximately 1 to 5, advantageously 2 to 3 hours and a heating rate of approximately 10 ° C./min to approximately 50 ° C./min, in particular approximately 20 ° C./min to approximately 40 ° C./min, is advantageous about 35 ° C / min to about 45 ° C / min, where the heating rates relate to the temperature of the furnace. The heating rates can be effected in batch heat treatment by a corresponding, controlled heating of the furnace or in a continuous process by controlling the feed rate of the substrates through a tunnel furnace which is operated with a fixed temperature profile.

In one embodiment of the method described, the substrate is moistened before being arranged on the coating device. When dry, the substrates have a high pumping speed for liquids. In particular when coating high-cell substrates with cell densities of 120 cm ^-2 and above, this can lead to a solidification of the coating medium and a blockage of the flow channels even during filling. It is therefore advantageous to moisten the substrates before coating. This can also be a pre-impregnation with acids, bases or salt solutions. The pre-impregnation facilitates the formation of the coating on the channel walls according to the sol-gel method. The pH of the dispersion is shifted by the contact of the coating dispersion with the pre-impregnated channel walls. As a result, the dispersion is converted into a gel.

In a further embodiment of the described method, the displacement body acts on the coating medium in such a way that a volume of the coating medium which is proportional to the movement of the displacement body displaces and a corresponding increase in the fill level of the coating medium in the coating device is effected until a first fill level of the coating medium in the coating device is reached. This first fill level is determined so that the same liquid level is always present in the coating device before the beginning of each coating process of a substrate, so that a reproducible coated length of the channels can be achieved even with a decreasing amount of liquid coating medium. Reaching the first fill level can be determined by a signal triggered by the sensors (123, 223).

After the first filling level of the coating medium has been reached, the volume of coating medium required for coating the substrate (i.e. the coating for coating the inside of the channels of the substrate up to the desired coated length of the channels) is introduced into the channels. For this purpose, the displacement body acts on the coating medium in such a way that a volume of the coating medium proportional to the movement of the displacement body displaces and causes a corresponding increase in the fill level of the coating medium in the coating device, that is to say the penetration of the coating medium into the channels of the substrate up to the desired fill level or coated length of the channels proportional to the displaced volume until a second fill level of the coating medium is reached in the coating device. A sensor can determine when the second fill level has been reached. While the first fill level of the coating medium is within the coating device (122, 222), the second fill level of the coating medium is either inside the substrate (121, 221), or at least on the same level, but preferably above the upper end face of the substrate ( 121, 221). If the second fill level is inside the substrate, a coated length of the substrate is achieved which is less than its axial length L. If the second fill level of the coating medium is on the same level, but preferably above the upper end face of the substrate (121, 221), the inside of the channels of the substrate is coated over the entire axial length L.

The control of the second fill level is advantageously carried out by a sensor, however, only for calibration, that is to say the setting of the parameters for controlling the arrangement. Once these parameters are known, substrates of the same type can be coated in a reproducible manner with the same parameters without monitoring the second fill level with a sensor during each coating process.

The (excess) coating medium is then removed from the channels of the substrate, the coating being in the Channels. The substrates obtained are then optionally dried and subjected to a heat treatment as described above.

• Bereitstellen des Substrates;
• Bereitstellen einer Anordnung gemäß der Erfindung;
• Anordnen des Substrates auf der Beschichtungsvorrichtung;
• Auslösen der Bewegung des Kolbens, so dass die vom Kolben verdrängte Flüssigkeit den Verdrängungskörper proportional zur Menge des verdrängten Flüssigkeitsvolumens bewegt;
• Einwirken des Verdrängungskörpers auf das Beschichtungsmedium, wobei ein der Bewegung des Verdrängungskörpers proportionales Volumen des Beschichtungsmediums verdrängt und ein entsprechender Anstieg des Füllstandes des Beschichtungsmediums in der Beschichtungsvorrichtung bis zu einem ersten Füllstand des Beschichtungsmediums bewirkt wird;
• Feststellen des Erreichens des ersten Füllstands des Beschichtungsmediums;
• Erneutes Auslösen oder fortgesetzte Bewegung des Kolbens, so dass die vom Kolben verdrängte Flüssigkeit den Verdrängungskörper proportional zur Menge des verdrängten Flüssigkeitsvolumens bewegt;
• Einwirken des Verdrängungskörpers auf das Beschichtungsmedium, wobei ein der Bewegung des Verdrängungskörpers proportionales Volumen des Beschichtungsmediums verdrängt und ein entsprechender Anstieg des Füllstandes des Beschichtungsmediums in der Beschichtungsvorrichtung bis zu einem zweiten Füllstand des Beschichtungsmediums bewirkt wird, wodurch das Eindringen des Beschichtungsmediums in die Kanäle des Substrates bis zur gewünschten Füllhöhe bzw. beschichteten Länge der Kanäle proportional zum verdrängten Volumen des Beschichtungsmediums erfolgt;
• Entfernen des Beschichtungsmediums aus den Kanälen des Substrates, wobei sich die Beschichtung in den Kanälen ausbildet.

A method for coating substrates can be carried out with the following steps:

• Providing the substrate;
• Providing an arrangement according to the invention;
• Placing the substrate on the coating device;
• Triggering the movement of the piston so that the liquid displaced by the piston moves the displacer in proportion to the amount of the displaced liquid volume;
• Action of the displacement body on the coating medium, displacing a volume of the coating medium which is proportional to the movement of the displacement body and causing a corresponding increase in the fill level of the coating medium in the coating device up to a first fill level of the coating medium;
• Determining when the first level of the coating medium is reached;
• Releasing or continuing movement of the piston so that the liquid displaced by the piston moves the displacer in proportion to the amount of liquid volume displaced;
• Action of the displacement body on the coating medium, displacing a volume of the coating medium which is proportional to the movement of the displacement body and a corresponding increase in the fill level of the coating medium in the coating device is brought about up to a second fill level of the coating medium, as a result of which the penetration of the coating medium into the channels of the substrate up to the desired filling height or coated length of the channels in proportion to the displaced volume of the coating medium;
• Removing the coating medium from the channels of the substrate, the coating forming in the channels.

The present invention was directed to substrates with reproducibly coated lengths of the channels with little variation in the coated lengths within the substrates.

The finished substrates suitable for the production of exhaust gas filters for motor vehicles (ie coated and heat-treated or calcined substrate) have a particularly uniform coating, which is characterized in that the coated lengths of the different channels between the channels are not more than 5 mm, in particular differ from each other by 3 mm, which applies to at least 95% of all channels of a substrate, advantageously at least 99% of all channels of a substrate, in particular to 100% of all channels. Defects can mean that the flow and pressure conditions of individual channels of a substrate deviate significantly from the other channels, which means that the liquid coating medium penetrates considerably more or more easily and under the coating conditions either to a lesser or greater length of the individual Channels is coated. In these cases, the desired uniform coating length can only be achieved for some of the channels, but generally for more than 95% of all channels. The coated length of the channels is smaller than the axial length L. The uniform coating length has the advantage that two coatings can be introduced in this way from the opposite end faces of the respective substrate. If these coatings are different and must be separate from one another (for example because the coating components react with one another in an undesirable manner or adversely affect one another), a distance must be maintained and reliably ensured between the two coatings. It is an advantage if the coating length can be set as accurately and reliably as possible, since only a small length of the substrate has to be used for the distance between the coatings, which remains uncoated and thus has no function. This can result in improved exhaust gas purification or the loading of the substrate with a coating can be reduced.

According to the invention, therefore, a coated substrate for producing exhaust gas filters for motor vehicles is provided, in which the channels are provided on the inside with at least a first catalytically active coating and a second catalytically active coating, the lengths coated with the first catalytically active coating and the second catalytically active coating of the channels is in each case smaller than the axial length L of the substrate and, for at least 95% of the channels of a substrate, the lengths of the channels respectively coated with the first catalytically active coating and the second catalytically active coating are not more than 5 mm, preferably 3 mm, from one another deviate, and the distance between the two coatings in at least 95% of the channels of a substrate is at most 5 mm, advantageously at most 3 mm, in particular at most 1 mm.

In Figures 3A and 3B Such a coated substrate (300) is shown. The substrate has two end faces (301), a lateral surface (302) and a length (L) and is crossed by a large number of channels (310) between the end faces. The channels are provided with a first coating (330) on a first partial length (303) and with a second coating (340) on a further partial length (305) Figure 3A shown with thickened lines, which form two zones, each provided with a first and a second coating. The distance (304) between the two zones (303, 305) is preferably minimized, for which purpose a coating length that is as uniform as possible is required in both zones (303, 305) in order to avoid an overlap. According to this invention, this coating-free distance (304) is a maximum of 5 mm, advantageously a maximum of 3 mm, in particular a maximum of 1 mm. In this Figure 3A a substrate (300) with circular end faces is shown. The end faces can of course also have a rectangular, square, oval, triangular, hexagonal or other polygonal shape, which results in a correspondingly different spatial shape of the substrate, such as a prismatic or cuboid shape.

The partial lengths provided with the first (330) and the second (340) coating can be the same or different.

The type of the first and the second coating are advantageously different. In one embodiment of the invention, at least one of the coatings is an oxidation catalyst or an SCR catalyst. In a particularly advantageous embodiment of the invention, the first coating (330) is an SCR catalyst and the second coating (340) is an oxidation catalyst.

The oxidation catalyst advantageously contains a noble metal from Group VIII of the Periodic Table of the Elements such as platinum, palladium, ruthenium, rhodium, gold, iridium or mixtures thereof, advantageously on a porous solid support, usually a porous inorganic oxide such as aluminum oxide or silicon dioxide. Platinum on a porous aluminum oxide as a carrier is particularly advantageous. This coating on the coated substrate generally has an amount of 0.1 to 10 g / ft ³ platinum.

In a specific embodiment of the invention, the SCR catalyst contains an oxide selected from the group consisting of titanium dioxide, vanadium pentoxide, tungsten trioxide, cerium oxide, zirconium oxide or mixtures thereof.

In a further specific embodiment of the invention, the SCR catalyst contains titanium dioxide as a matrix, up to 10% by weight of vanadium pentoxide and up to 20% by weight of tungsten trioxide.

In a further specific embodiment of the invention, the first coating contains an SCR catalyst containing vanadium pentoxide and aluminum oxide and the second coating contains an oxidation catalyst which contains platinum, gold, palladium and aluminum oxide. The second In this case, the coating preferably has an amount of 0.1 to 10 g / ft ³ of platinum, gold or combinations thereof

In a further specific embodiment of the invention, the first coating contains an SCR catalyst containing titanium dioxide, vanadium pentoxide and tungsten trioxide and the second coating contains an oxidation catalyst which contains platinum and aluminum oxide. In this case, the second coating preferably has an amount of 0.1 to 10 g / ft ³ of platinum.

In a further specific embodiment of the invention, the first coating contains an SCR catalyst containing a composition of a zeolite, in particular a zeolite exchanged with iron or copper, and the second coating contains an oxidation catalyst which contains platinum and aluminum oxide. In this case, the second coating preferably has an amount of 0.1 to 10 g / ft ³ of platinum.

In a further specific embodiment of the invention, the first coating contains an SCR catalyst containing an iron-exchanged beta zeolite with an ammonia storage capacity of at least 20 milliliters of ammonia per gram of catalyst material, and the second coating contains an oxidation catalyst which contains platinum and aluminum oxide. In this case, the second coating preferably has an amount of 0.1 to 10 g / ft ³ of platinum.

In a further specific embodiment of the invention, the first coating contains an SCR catalyst containing a composition of a zeolite, in particular a zeolite exchanged with iron or copper, and the second coating contains an oxidation catalyst which contains palladium and / or rhodium and aluminum oxide. In this case, the second coating preferably has an amount of 0.1 to 10 g / ft ³ of palladium, rhodium or combinations thereof.

The coated substrates suitable for the production of exhaust gas filters for motor vehicles generally have porosities of more than 40% from 40% to 75%, especially from 45% to 60%. The average pore sizes are at least 7 µm, for example 7 µm to 34 µm, preferably more than 10 µm, in particular 10 µm to 20 µm or 11 µm to 19 µm. Finished substrates which are suitable for producing exhaust gas filters for motor vehicles are particularly advantageous and have average pore sizes of 11 to 33 μm and porosities of 40% to 60%.

The cell densities of the substrates amount usually up to 700 or more per inch ² (square inch), with significantly lower cell densities are used, such as about 7 to 600, in particular 100 to 400 cells per inch ² (400 cells per inch ² correspond to about 62 cells per cm ² ), the shapes of the cells being rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shapes. The cell density is a measure of the number of channels per unit area of the top view, which run through the substrates parallel to the longitudinal axis. The wall thicknesses, i.e. the thickness of the walls that separate the channels from one another, are 0.002 and 0.1 inches (approximately 0.005 cm to approximately 0.25 cm), preferably 0.002 to 0.015 inches (approximately 0.005 cm to 0.038) cm). Advantageous substrates have a wall thickness of about 0.01 inch to 0.02 inch (about 0.0254 cm to 0.058 cm), preferably with a porosity of 40% to 60% and an average pore size of 10 µm to 20 µm.

Detailed description of the drawings:

Figure 1 (not according to the invention) shows an arrangement of the invention for coating channels (110) in a substrate (121), which has a piston (101), which is actuated by an actuator (100), in a cylinder (102), which Liquid (103) is filled and through a connection (104) of cylinder (102) with the displacement body (111) allows the actuation of the displacement body (111) in the container (112) which is filled with liquid coating medium (113) and two Has line sections (114, 116) with an intermediate multi-way valve (115) between the container (112) and the coating device (122), the coating device (122) with the substrate (121) and with sensors (123) for determining the first fill level (130) is provided. The displacement volume of coating medium (113) and the state of the displacement body (111) in the container (112) are checked with further sensors (124).

The values determined by the sensors (123, 124) are transmitted to a control unit (125), which in turn controls the actuator (100) and thus the piston (101).

The multi-way valve (115) on the one hand switches the filling of the coating device (122) to the first fill level (130) with coating medium (113) in the filling flow direction (117) and on the other hand after reaching the second fill level (132) in the substrate (121), in the return flow direction (118) the connection to the emptying pump (119) and to the connecting line (120) to a storage container for excess coating medium (113) and to keep it ready for further use.

All the necessary control commands for this are preferably also issued by the central control unit (125).

Figure 2 (not according to the invention) shows an arrangement of the invention for coating channels (210) in a substrate (221), which has a piston (201) actuated by an actuator (200) in a cylinder (202), which Liquid (203) is filled, and communicates through a connection (204) of cylinder (202) with the container (212), in which the displacement body (211) is located, which contains liquid coating medium (213) and which via two line sections ( 214, 216) with an intermediate multi-way valve (215) is connected to the coating device (222), which is provided with a substrate (221) and sensors (223) for determining the first fill level (230) of the coating medium (213).

With the further sensors (224) on the container (212), the displacement volume of coating medium or the state of the displacement body (211) in the container (212) is checked. The sensors (223, 224) determined values are transmitted to a control unit (225) which in turn controls the actuator (200) and thus the piston (201).

The multi-way valve (215) on the one hand switches the filling of the coating device (222) to the first fill level (230) with coating medium (213) in the filling flow direction (217) and on the other hand, after reaching the second fill level (232) in the substrate (221), in the return flow direction (218) the connection to the emptying pump (219) and to the connecting line (220) to a storage container for excess coating medium (213) and to keep it ready for further use. All the necessary control commands for this are preferably also issued by the central control unit (225).

Figures 3A and 3B show in perspective a substrate (300) which has a cut break in three planes in its middle part in order to provide an insight into the coating structure according to the invention.

The substrate (300) coated in two partial length zones (303, 305) has two end faces (301), a lateral surface (302) and a length (L) and is made up of a large number of channels (310) between the two end faces (301 ) pulled through.

A first coating (330) is applied to a first partial length zone (303) in the channels (310), while a further partial length zone (305) is provided with a second coating (340).

Between the two partial length zones (303) and (305) respectively. Between the two coatings (330) and (340) there is a coating-free zone (304), like this in particular Figure 3B shows enlarged.

Brief description of the drawings

• Fig. 1 (not according to the invention):
  • 100 actuator
  • 101 pistons
  • 102 cylinders
  • 103 liquid
  • 104 connection
  • 110 channels - in the substrate 121
  • 111 displacement body
  • 112 containers
  • 113 coating medium
  • 114 line section
  • 115 multi-way valve
  • 116 line section
  • 117 Filling flow direction
  • 118 Reverse flow direction, for removing coating medium 113
  • 119 Drain pump
  • 120 connecting line to the reservoir of the coating medium
  • 121 substrate
  • 122 coating device
  • 123 sensor for detecting the fill level 130
  • 124 Sensor for monitoring the position of the displacer 111
  • 125 control unit
  • 130 First level - out of 113 in the coating device 122
  • 132 second level - from 113 in substrate 121
• Fig. 2 (not according to the invention):
  • 200 actuator
  • 201 pistons
  • 202 cylinders
  • 203 liquid
  • 204 connection
  • 210 channels - in the substrate 221
  • 211 sinker
  • 212 containers
  • 213 coating medium
  • 214 line section
  • 215 multi-way valve
  • 216 line section
  • 217 direction of filling
  • 218 suction flow direction of 213
  • 219 Drain and suction pump
  • 220 Connection line to the reservoir for excess coating medium 213
  • 221 substrate
  • 222 coating device
  • 223 Sensor for detecting the fill level 230
  • 224 Sensor to monitor the position of the sinker
  • 225 control unit
  • 230 First fill level - in the coating device 222
  • 232 second fill level - in the substrate 221
• Fig. 3 :
  • 300 substrate
  • 301 end face
  • 302 outer surface
  • 303 First partial length zone
  • 304 distance - between the two partial lengths 303 and 305
  • 305 Second partial length zone
  • 310 channels - 300 in the substrate
  • 330 First coating - in channels 310
  • 340 Second coating - in channels 310
  • L length - total of substrate 300
• Fig. 4 (not according to the invention): 401 to 407 denote the seven process steps according to claim 5
• Fig. 5 (not according to the invention): 501 to 509 denote the nine process steps according to claim 6

example 1

Flow-through honeycomb bodies with a length of 101.6 mm and an oval cross section with a minor axis of 86 mm and a major axis of 131 mm and a cell density of 62 cm ^-2 made of cordierite are obtained with a suspension of platinum supported on aluminum oxide (obtained according to Example 1) EP 957064 ) coated in water with a solids content of 35% by weight as the coating medium. There is an arrangement for this Figure 2 used. The coating height is 45.8 mm. After coating, the coated substrates are dried with an air stream of 100 ° C. and calcined at 500 ° C. For every thousandth coated support body, the coated length is determined by X-ray coating and the coated lengths of the channels are determined using digital image evaluation and the difference between the respective maximum and minimum lengths is formed. The difference is always less than 3.0 mm. 200 coated supporting bodies are examined. The coating device after Figure 2 will continue to operate. No interruption to maintenance or repair is required to complete 325,000 coating operations.

Example 2

The procedure was as in Example 1, but an arrangement was followed Figure 1 used. The differences between the maximum and minimum lengths were always less than 2 mm. 170 coated supporting bodies are examined. No maintenance or repair interruption is required to complete 225,000 coating operations.

Claims (1)

1. Coated substrate (300) for producing exhaust filters for motor vehicles, in which the channels (310) are provided internally with at least one catalytically active coating, the coated length (303) of the channels (310) is smaller than the axial length L of the substrate, and the coated length of the channels (303) does not differ by more than 5 mm in at least 95% of the channels of a substrate (310), wherein the channels (310) are provided internally with at least a first catalytically active coating (330) and a second catalytically active coating (340), the lengths of the channels (303, 305) coated with the first catalytically active coating (330) and the second catalytically active coating (340) is respectively smaller than the axial length L of the substrate, and the lengths of the channels respectively coated with the first catalytically active coating (330) and the second catalytically active coating (340) differ from one another by no more than 5 mm in at least 95% of the channels of a substrate (310); and wherein the distance between two coatings (304) is at most 5 mm in least 95% of the channels of a substrate.

Images